Search

A synchronous reduction and assembly strategy is designed to fabricate large-area graphene films and patterns with tunable transmittance and conductivity. Through an oxidation-reduction reaction between the metal substrate and graphene oxide, graphene oxide is reduced to chemically converted graphene and is organized into highly ordered films in situ. This work will form the precedent for industrial-scale production of graphene materials for future applications in electronics and optoelectronics.

Fabricating free-standing, three-dimensional (3D) ordered porous graphene structure can service a wide range of functional materials such as environmentally friendly materials for antibacterial medical applications and efficient solar harvesting devices. A scalable solution processable strategy is developed to create such free-standing hierarchical porous structures composed of functionalized graphene sheets via an “on water spreading” method. The free-standing film shows a large area uniform honeycomb structure and can be transferred onto any substrate of interest. The graphene-based free-standing honeycomb films exhibit superior broad spectrum antibacterial activity as confirmed using green fluorescent protein labeled Pseudomonas aeruginosa PAO1 and Escherichia coli as model pathogens. Functional nanoparticles such as titanium dioxide (TiO2) nanoparticles can be easily introduced into conductive graphene-based scaffolds by premixing. The formed composite honeycomb film electrode shows a fast, stable, and completely reversible photocurrent response accompanying each switch-on and switch-off event. The graphene-based honeycomb scaffold enhances the light-harvesting efficiency and improves the photoelectric conversion behavior; the photocurrent of the composite film is about two times as high as that of the pure TiO2 film electrode. Such composite porous films combining remarkably good electrochemical performance of graphene, a large electrode/electrolyte contact area, and excellent stability during the photo-conversion process hold promise for further applications in water treatment and solar energy conversion.

Flexible, paper-based graphene and graphene oxides are now emerging as a new class of materials with a variety of applications in electrochemical devices, novel composites, antibacterial agents, separation membranes, and so on. But the tight layer and the poor permeability limit their applications in the fields requiring permeable layers and tunable layer spacing. We demonstrate that the temperature-dependent decomposition reaction of ammonium nitrate can be utilized to modulate the layer spacing of graphene oxide paper and modify its permeability. Unlike the commonly used intercalation method, our strategy enables the layer spacing of the paper to be expanded over large range (123%–20 000%) and avoids the occupation of layer room by guest molecules. Dependent on the expansion amplitude, the papers exhibit a variety of interesting applications, including the highly efficient exclusion of small organic molecules, the separation of ultrathin nanoparticles, and the loading of polar and nonpolar guest molecul...

Thin proton conductive electrolyte membrane of BaCe0.85Y0.15O3-α(BCY15) was deposited on porous green NiO-BCY15 substrate by the modified spin-coating method. The dense, crack-free BCY15 electrolyte layers with thickness of ca. 30αm were obtained after the green bi-layers were co-sintered at 1400for 5h. With Ba0.5Sr0.5Co0.8Fe0.2O3-α as the cathode, membrane reactor for ammonia synthesis at atmospheric pressure was assembled. The membrane reactors were characterized by field-emission scanning electron microscope (FESEM), X-ray diffraction (XRD) and electrochemical AC impedance. Peak ammonia formation rate of about 4.1×10.9 mol s-1 cm-2 was achieved with imposed DC current 1mA at 530 with the BCY15 membrane reactor.

Through the direct reaction of the aqueous solutions of zinc salts and KOH, highly uniform ZnO multipods consisted of rod-shaped branches are synthesized in an extremely high yield. The synthesis is conducted at low temperature, does not require any organic capping agents to affect the crystal habit, and is independent on the species of zinc sources. Moreover, by changing the reaction temperature from 25 to 70 °C, the tips of the multipods can be adjusted from taper to regular hexagon. The mechanism responsible for the formation of ZnO multipods is the self-regulation growth guided by the inherently asymmetric structure of hexagonal ZnO along the c -axis. After the surface modification with amino groups, ZnO multipods show good affinity to Ag and Au nanoparticles, which results in the spontaneous migration of Au and Ag nanoparticles to the surface of ZnO to form well-defined Au/ZnO and Ag/ZnO heterostructures. The fabricated hybrids are found to be effective surface-enhanced Raman scattering (SERS) substrates because of their distinct geometrical shape, large surface area, and the ability to create a strong local electromagnetic field by the metal–semiconductor heterojunction.

High-yield ternary ZnO/ZnS/γ-Fe 2 O 3 hollow spheres with an average size of 600 nm were prepared rapidly via a microwave-irradiation route; the reaction period is as short as 30 min. The hollow spheres are composed of numerous ZnO, ZnS, and γ-Fe 2 O 3 crystallites and the mechanism responsible for their formation is Ostwald ripening. Every hollow sphere has a distinct surface hole with the pore size of tens of nanometers or hundreds of nanometers. The characterizations of the physical properties of the hollow spheres reveal that they have integrated the superparamagnetism of γ-Fe 2 O 3 and the photoluminescence property of ZnO and ZnS. Furthermore, since the pore size of the hole on the surfaces of the hollow spheres is large enough to accommodate bovine serum albumin (BSA) molecule with a giant size, the hollow spheres can not only adsorb BSA with their external surfaces but also trap the proteins in their interiors. Per gram hollow sphere can immobilize 178.6 ± 34.5 mg of BSA when they are interacted with 600 μg/mL BSA solution for 24 h. The investigations on the releasing behavior of BSA by the hollow spheres reveal that BSA molecules on the external surfaces of the spheres are desorbed quickly, while those confined in the interiors of the spheres are released smoothly and the process is sustained over 10 days. The accumulative releasing percentage of BSA is about 51% in 10 days.

Titanate nanotube bundles assembled by several simple nanotubes were synthesized through a simple reaction between TiO 2 crystallites and highly concentrated NaOH in the presence of Au or Pd sols. Due to the unique scrolling growth mechanism of titanate nanotubes (TNTs), Au or Pd clusters were encapsulated in situ by TNTs, and titanate/Au and titanate/Pd nanotube bundles were formed. In comparison with carbon nanotubes (CNTs) or active carbon that was widely used as carriers to support metal clusters, TNTs bundles can immobilize the metal clusters tightly and overcome the shortcoming of exfoliation of metal clusters from the carriers. The as-prepared titanate/metal hybrids possess mesoporosity and high surface area. The electrochemical oxidation of methanol demonstrates that titanate/Pd hybrids exhibit high electrocatalytic activity and excellent stability, and hence they should be ideal catalyst candidates in direct methanol fuel cells (DMFCs).

Diverse multipod-shaped CdSe nanocrystals with a high yield and good crystallinity were synthesized via microwave irradiation route, which only needed a period of 10 min. Cd(NO 3 ) 2 and selenium powders were used as raw materials in the preparation, which were safer and greener relative to the commonly used trioctylphosphine-based precursors for synthesizing CdSe tetrapods. By selectively introducing organic additives into the system, the morphology of CdSe nanocrystals could vary from tetrapods to hexapods, octapods, and more complex multipods. The possible growth mechanisms of the multipods were discussed based on the investigations on the structure and shape of intermediates. The present microwave irradiation route should provide an alternative to the rapid and controllable growth of other important selenides with distinct morphologies.

In this paper, we demonstrated the encapsulation of CdTe quantum dots (QDs) and ZnO nanorods (NRs) with a layer of mesoporous SiO2 shell (pore size: 4.1 nm) for the purpose of integrating dual-emission property into one common nanostructure. Within the core−shell CdTe/ZnO@SiO2 nanocomposites, CdTe QDs and ZnO NRs provide visible emission and UV emission, respectively. The fluorescence intensity ratio of the dual emission can be tuned by altering the hydrolysis time of tetraethyl orthosilicate (TEOS). The core−shell CdTe/ZnO@SiO2 nanocomposites exhibit very interesting photoluminescent behaviors after interactions with heavy-metal ions such as Hg2+, Pb2+, and Cu2+. The visible emission contributed by CdTe QDs was abnormally enhanced in a range of 20−90% at the concentration of Hg2+ < 10−8 M, Pb2+ < 10−5 M, and Cu2+ < 10−6 M, whereas the intensity of UV emission by ZnO NRs was kept constant in all cases. Consequently, the UV emission may serve as a reference. The mechanism of the fluorescence enhancement is...

A large-area, nest-like ZnO nanowires (NWs) array was prepared through the oxidation reaction between zinc foil and (NH4)2S2O8 at 150 °C for 18 h. CdTe quantum dots (QDs) were linked chemically to the array to form CdTe/ZnO heterostructures based on the good affinity of carboxyl to zinc ions. The molar content of CdTe in the heterostructures can be controlled at the level of 1.2%, 5.1%, and 11.4%, which depends on the soaking time of ZnO array in CdTe solution. The measurements of the optical properties of the as-prepared CdTe/ZnO heterostructures reveal that they can harvest incident lights more efficiently than can unmodified ZnO NWs arrays, whose reflectance was decreased about 20%. The good light-trapping effect and the attachment of CdTe QDs significantly improve the photovoltaic properties of the heterostructure and result in a good rectifying behavior. The photoanode based on the heterostructures has open-circuit voltages of 0.5−0.6 V and a short-circuit current of 0.3 mA/cm2.

By scarifying ZnO crystallites within core–shell-structured ZnS/ZnO microspheres, hollow spheres of ZnS on a gram scale were prepared, which did not require spherical colloids, vesicles, or microemulsions as the templates. The synthesis was performed at a relatively low temperature (

This manuscript describes the low-temperature, solution-based doping of Mn2+ ions into colloidal ZnO nanorods, and the yield of the products is in a gram scale. The structures and chemical compositions of the products were characterized by XRD, XPS, EDS, and FT-IR spectroscopy. The results demonstrate that Mn2+ ions were successfully incorporated into the lattice position of Zn2+ ions in ZnO. The concentration of Mn2+ ions (in molar %) in the products can be controlled in the range of 1.25∼5%. The surfaces of Mn-doped ZnO nanocrystals have very rich hydroxyl groups, which enhance their solubility in many polar and nonpolar solvents. TEM and FESEM were used to characterize the morphology of ZnO and Mn-doped ZnO nanocrystals, and they revealed that both the undoped and doped ZnO nanocrystals are composed of uniform nanorods with a diameter of 8 nm and a length of 95 nm. The doping of Mn2+ ions has significant influences on the optical properties of ZnO nanorods. UV−vis absorption spectroscopy measurements r...

This manuscript describes a self-organization method for the large-scale production of porous ZnS/ZnO composite microspheres and their application as supports of CdTe quantum dots. Through the reaction of Zn 2+ and urea and thioacetamide at 85 °C for 10 min, nanoparticles of cubic ZnS and amorphous ZnO were formed and they present a strong tendency to organize into regular microspheres. The formation of nanopores within the microspheres is related to Ostwald ripening: some small nanoparticles within the microspheres were merged by the larger ones, and as a result, numerous nanopores were generated. Furthermore, when a solvothermal ripening is applied for the porous microspheres, the components within them can be transformed into hexagonal ZnS and ZnO. CdTe quantum dots were introduced into the nanopores to achieve luminescent microspheres through in situ nucleation and growth. And it is expected that, besides semiconducting quantum dots, other functional units, such as magnetic and catalytically activated nanoparticles, can also be introduced into them.

This manuscript describes a simple, environmentally friendly strategy for the rapid and large-scale growth of ultralong nanowires and nanoribbons of wurtzite CdTe. The nanowires and nanoribbons were prepared through the direct hydrothermal treatment of CdTe nanoparticles precoated on ⟨100⟩ Czochralski silicon, which did not involve complicated reactions. The well-crystalline nanowires and nanoribbons were grown along the [102] direction and were up to 100 μm long. The growth of the nanowires and nanoribbons was dominated by the mechanism of oriented attachment, which was clarified through the tracing of the temporal evolution of CdTe nanoparticles coated on the silicon substrate in the process of hydrothermal treatment. Furthermore, the proposed strategy was also effective in the preparation of anisotropic nanostructures of other II−IV group compounds (e.g., ZnO and CdSe).

Morphology-controlled growth of nanomaterials is an important topic in nanosciences because it is the prerequisite of the applications of nanomaterials. In this work, we reported the microwave-enhanced rapid and green synthesis of Sb 2 Se 3 nanorods with a flat cross section through the reaction between selenium powders and sodium antimony tartrate. Microwave irradiation greatly shortened the reaction time, which made the cycle to be as short as 30 min. The intrinsic mechanism for the formation of nanorods with a flat cross section is related to the direction of the unique layer-structured structure of orthorhombic Sb 2 Se 3 .

This manuscript described a two-step method to fabricate nanocomposites composed of ZnFe2O4 nanoplates and Ag nanoparticles, which exhibit a good photocatalytic activity. ZnFe2O4 nanoplates were firstly synthesized through the co-precipitation reaction of Zn2+ and Fe3+ in the solution containing urea and oleic acid. Ag nanoparticles were introduced into the nanoplates through the reduction reaction of silver nitrate by ethylene glycol. The content and size of Ag nanoparticles were adjusted through the control of the reflux time of silver nitrate in ethylene glycol. Studies on the photocatalytic activity of Ag@ZnFe2O4 nanocomposites revealed that the irradiation of Xe lamp could drive them to induce the rapid decomposition of Rhodamine B. And the degradation rate was speeded as the increase of Ag weight content in the composite structure. The good photocatalytic activity of Ag@ZnFe2O4 nanocomposites was attributed to their unique structure, which can direct the flowing of electrons and holes towards opposite directions.

This work describes the synthesis and magnetic–optical properties of Fe 3 O 4 nanowires decorated by CdTe quantum dots. The composite nanowires with a length of 1 μm and an average diameter of 23±3 nm were prepared in a high yield through the preferential growth of Fe 3 O 4 on CdTe quantum dots using ethylenediamine as template. Their growth mechanism was discussed based on the results of control experiments. Studies on the optical and magnetic properties of the composite nanowires reveal that they assume not only yellow-green emission feature but also room temperature ferromagnetism.

We proposed a general and highly efficient wet strategy for the fabrication of ordered anisotropic nanostructures on the solid substrate. The method involves the pre-deposition of colloidal precursors onto the surface of the silicon substrate and the subsequent hydrothermal crystallization. In the process of crystallization, the colloidal precursors can develop into distinct shapes. The use of the substrate can promote the nucleation and the occurrence of anisotropic growth and induces the products to grow into ordered structures. With this method, regular ZnO nanoellipsoids, SnO 2 and Cd(OH) 2 nanorod clusters, and Bi 2 S 3 nanowires were prepared readily. The growth processes of the four regular nanostructures were studied through the investigations of the morphology of precursors and intermediates.

High-quality Cu3Se2 nanoplates were synthesized in a large scale through microwave-enhanced reaction between selenium and copper(I) oleate. The nanoplates are approximately round with thickness of 17 nm and the diameter in the range of 700∼1000 nm. The distinct shape of the nanoplates provides an ideal site for combining functional units, and as an example, carboxyl-terminated CdTe quantum dots were adsorbed onto Cu3Se2 nanoplates to form Cu3Se2−CdTe nanocluster by the chemical linkage of carboxyl to Cu. The fabricated nanoclusters exhibit an enhanced photovoltaic property (i.e., large photocurrent and short response time). Furthermore, this work provides a rational method to the design and fabrication of quantum dots decorated semiconductor nanocomposites.

In this manuscript we have demonstrated a template-free route to the preparation of hollow In 2 S 3 nanospheres by solvothermally treating solid In 2 S 3 spheres comprised of small particles at 180 °C for 24 h. This method is simple but highly efficient, which can transform the solid precursors into hollow nanostructures in an extremely high yield. Investigations into the intermediates reveal that the formation of hollow spheres is through the mergence of the smaller particles within the solid spheres by the relatively large ones in the ripening process (i.e., Ostwald ripening). The well crystalline hollow nanospheres have the diameters of 40–70 nm and an average wall thickness of 7 nm. Due to the closeness of the size of hollow nanospheres to the Bohr radius (33.8 nm) of the excition in In 2 S 3 , an obvious quantum size confinement and morphology-dependent property are observed. Hollow In 2 S 3 nanospheres show an intense absorption between 318 and 512 nm, which is blue-shifted to shorter wavelengths relative to that of bulk In 2 S 3 . Hollow In 2 S 3 nanospheres also exhibit a strong photoluminescence. The green band centered 518 nm is due to the band-band transitions and the orange emission centered at 624 nm originates from the indium interstitial defect. These hollow In 2 S 3 nanospheres could be used as a distinctive multicolored phosphor and material for producing photoelectrochemical devices.

A simple and convenient Ostwald ripening route to the morphology- and phase-controlled preparation of hollow Sb2S3 microspheres is developed. The hollow spheres are clusters of smaller microspheres if orange amorphous Sb2S3 colloid is used as the precursor, whereas, if starting from the yellow precursor, the products are regular hollow spheres. By selecting appropriate experimental conditions for ripening, the phase of the hollow Sb2S3 microspheres can be controlled. Amorphous and orthorhombic hollow spheres are prepared by ripening the colloidal precursors at ambient temperature and in an autoclave, respectively. The closed shell of hollow Sb2S3 spheres can be easily eroded by hydrochloric acid to form an open structure. By the in situ reduction of adsorbed Ag+ on the surface and interior of the hollow spheres, Ag nanoparticles are introduced into them, to form functional metal–semiconductor composites, the weight content of which is controlled by regulating the concentration of the Ag+ source and the adsorption time. The composite structures composed of Ag nanoparticles and hollow Sb2S3 spheres exhibit a remarkably enhanced absorption covering the UV and visible regions of the electromagnetic spectrum. A study of the photocatalytic properties of the composite structures demonstrates that exposure to both UV and visible light enables them to induce the rapid decomposition of 2-chlorophenol. The degradation rate increases with a larger weight content of Ag in the composite structure.

Starting from the polymeric structure of Sb 2 S 3 , we successfully prepared sub-micron-sized hollow cones of Sb 2 S 3 in a yield close to 85% via a solvothermal crystallization route. The quasi-2D ribbon-like structure of Sb 2 S 3 can direct the formation of thin crystal flakes, which can transform into hollow cones through a spiral rolling-up process favored by the high pressure generated in the solvothermal environment. Techniques such as XRD, SEM, TEM, SAED, EDAX, and HRTEM were used to characterize their morphology, structure, and composition. This crystallization route is also workable for the preparation of tubular Bi 2 S 3 , and we believe that it could be extended to the preparation of novel tubes of other materials with an analogous chain structure, such as selenium and tellurium.

We have described the large-scale preparation of uniform nanowires, networks built by “Y” nanowire junctions, and the mixture of microspheres and hexagonal prisms of trigonal selenium via vapor phase deposition routes. The principles of the experiments were based on the unique physical properties of trigonal selenium and its highly anisotropic crystal structure. The products were characterized by field emitting scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and electron diffraction. Investigations into the intermediate process in the formation of the products reveal that (i) networks built by “Y” nanowire junctions formed in a vapor−solid process were developed from triangular nanocrystals; (ii) the formation of uniform nanowires in a vapor−liquid−solid process is associated with chainlike structures composed of solidified droplets; and (iii) hexagonal prisms were formed through the gradual evolution of microspheres. On the basis of experimental facts, we conclude some ...

Without the assistance of any templates and organic additives, orthorhombic antimony sulfide (Sb 2 S 3 ) dendrites were obtained rapidly (3 h) through the crystallization of amorphous colloidal microspheres. The top view of dendrites reveals that their side branches are tetragonal prisms with a smooth face and nearly uniform breadth. The investigations on the growth mechanism demonstrated that the intermediate steps in the formation of dendrites are the rods and the structures with tip splitting. The kinetics of crystal growth, the anisotropic crystal structure and H + ions in the solution are believed to be responsible for the tip splitting. The structures with tip splitting subsequently grew and developed into dendrites eventually. A prolonged crystallization time (10 h) was found to be unfavorable to the further increase of dendrite size but led to its fragmentation.

Junction structures of copper nanorods with a high yield and uniform morphology were prepared using a novel soft template, which consisted of poly (ethylene glycol) and cetyltrimethylammonium bromide. X-ray diffractometer, transmission electron microscope and field emitting scan electron microscope studies of the phase, microstructure and morphology of the products were carried out. The absorption spectrum of the product showed an obvious red-shift due to the nanorod junction feature.

With the control of G1 poly(amidoamine) (PAMAM), an evolutionary course of stable colloidal silver from discrete nanoparticles to solid spheres through ultraviolet irradiation reduction of silver nitrate solutions was observed by transmission electron microscopy (TEM). The morphologies of the products depend on the Ag+ concentration. A mechanism of globular assembly was put forward to interpret the evolution of the nanostructures. Powder X-ray diffraction (XRD), electron diffraction (ED) patterns, and X-ray photoelectron spectroscopy (XPS) indicate the presence of cubic symmetry silver. XPS and Fourier transform infrared (FT-IR) spectroscopy confirm that dendrimers have participated in the stabilization and control of Ag nanostructures. In the UV–vis spectra, the intense surface plasmons are centered at 425 and 430 nm corresponding to the shapes of dots and solid spheres, respectively. The solid spheres exhibit excellent catalytic efficiency on the reduction of 2,7-dicholoroflurescein (DCF).

Ordered submicron ferromagnetic Co–B arrays were obtained through a biomimetic process at ambient temperature. When Co2+ ions complexed to soluble starch were reduced by potassium borohydride in a magnetic field, the magnetic force allowed the nanoparticles of Co–B alloys to array along the field lines and deposit on a solid support. This process is inspired by the migration mechanism of magnetotactic bacteria in a geomagnetic field and this convenient strategy should be helpful for the production of ordered arrays of other magnetic materials. After Co–B alloys are assembled into ordered chains, they exhibit strong ferromagnetic signals in the variable temperature ferromagnetic resonance spectra in the temperature range of 100–420 K.

Rational assembly of carbon nanostructures into large-area films is a key step to realize their applications in ubiquitous electronics and energy devices. Here, a self-assembly methodology is devised to organize diverse carbon nanostructures (nanotubes, dots, microspheres, etc.) into homogeneous films with potentially infinite lateral dimensions. On the basis of studies of the redox reactions in the systems and the structures of films, the spontaneous deposition of carbon nanostructures onto the surface of the copper substrate is found to be driven by the electrical double layer between copper and solution. As a notable example, the as-assembled multiwalled carbon nanotube (MWCNT) films display exceptional properties. They are a promising material for flexible electronics with superior electrical and mechanical compliance characteristics. Finally, two kinds of all-solid-state supercapacitors based on the self-assembled MWCNT films are fabricated. The supercapacitor using carbon cloth as the current collector delivers an energy density of 3.5 Wh kg−1 and a power density of 28.1 kW kg−1, which are comparable with the state-of-the-art supercapacitors fabricated by the costly single-walled carbon nanotubes and arrays. The supercapacitor free of foreign current collector is ultrathin and shows impressive volumetric energy density (0.58 mWh cm−3) and power density (0.39 W cm−3) too.

By taking advantage of the structural affinity between bismuth oxohalide and TiO₂, we successfully prepare a family of hybrid frameworks via the designated growth of bismuth oxohalide nanoplates on TiO₂ nanoribbons, and propose them as sunlight-driven bifunctional photocatalysts for all-weather removal of pollutants. The structural variability of bismuth oxohalide allows the optical absorption of the hybrid framework to be monotonically tuneable across the visible spectrum. Meanwhile, the hybridization greatly increases the surface roughness of the frameworks and enables the frameworks to harvest more photons to participate in photocatalytic reactions. Furthermore, the hybridization establishes two potential gradients to promote the separation of photo-induced electron-hole pairs: the internal electrical field perpendicular to the wide surfaces of bismuth oxohalide nanoplates and across the semiconductor-semiconductor heterojunction. Owing to the synergetic effects of the permeable mesoporous architecture, the intense visible light absorption, and the efficient charge separation, the hybrid frameworks are capable of all-weather removal of pollutants: they utilize the inter-ribbon pores to gather pollutants in the dark (behaving as collectors) and they rapidly degrade the pollutants in the day (behaving as photocatalysts). In particular, the BiOBr@TiO₂ framework exhibits very impressive sunlight-driven photocatalytic activity, which is much higher than commercially available P25 TiO₂ under the same conditions.

We describe a synchronous reduction and assembly procedure to directly produce large-area reduced graphene oxide (rGO) films sandwiched by a high density of metal nanoparticles (silver and copper). Further, by using the sandwiched metal NPs as sources, networks consisting of AgTCNQ and CuTCNQ nanowires were deterministically grown from the rGO films, forming structurally and functionally integrated rGO/metal-TCNQ hybrid films with outstanding flexibility, bending endurance, and electrical stability. Interestingly, due to the p-type nature of the rGO film and the n-type nature of the metal-TCNQ NWs, the hybrid films are essentially thin-film p–n junctions which are useful in ubiquitous electronics and optoelectronics. Measurements of the optoelectronic properties demonstrate that the rGO/metal-TCNQ hybrid films exhibit substantial photoconductivity and highly reproducible photoswitching behaviours. The present approach may open the door to the versatile and deterministic integration of functional nanostructures into flexible conducting substrates and provide an important step towards producing low-cost and high-performance soft electronic and optoelectronic devices.

Graphene nanosheets and metal nanoparticles (NPs) have been used as nano-building-blocks for assembly into macroscale hybrid structures with promising performance in electrical devices. However, in most graphene and metal NP hybrid structures, the graphene sheets and metal NPs (e.g., AuNPs) do not enable control of the reaction process, orientation of building blocks, and organization at the nanoscale. Here, an electrophoretic layer-by-layer assembly for constructing multilayered reduced graphene oxide (RGO)/AuNP films and lateral micropatterns is presented. This assembly method allows easy control of the nano-architecture of building blocks along the normal direction of the film, including the number and thickness of RGO and AuNP layers, in addition to control of the lateral orientation of the resultant multilayered structures. Conductivity of multilayered RGO/AuNP hybrid nano-architecture shows great improvement caused by a bridging effect of the AuNPs along the out-of-plane direction between the upper and lower RGO layers. The results clearly show the potential of electrophoretic build-up in the fabrication of graphene-based alternately multilayered films and patterns. Finally, flexible supercapacitors based on multilayered RGO/AuNP hybrid films are fabricated, and excellent performance, such as high energy and power densities, are achieved.

8 ] has been made over the past few decades. Such optical sensors are normally based on the simple measurement of the UV/Vis spectrum, fl uorescence spectrum, or colorimetry. Colorimetric detec-tion, which is visually and simply read out by the naked eye, is particularly attractive for point-of-use applications. What has limited such a colorimetric approach based on organic chromophoric probes is the narrow selectivity, solubility, and detection range. Recently, colorimetric detection based on Au nanopar-ticles (NPs) has drawn much attention

We demonstrate the engineered growth of TiO(2) nanotube arrays on flexible carbon fibre sheets. The modification not only enables the textile to absorb ultraviolet light efficiently but also imparts large surface area and mesoporosity to the textile. This flexible nanoarchitecture greatly facilitates the purification of organic wastewater.

Titanate nanotube bundles assembled by several simple nanotubes were synthesized through a simple reaction between TiO 2 crystallites and highly concentrated NaOH in the presence of Au or Pd sols. Due to the unique scrolling growth mechanism of titanate nanotubes (TNTs), Au or Pd clusters were encapsulated in situ by TNTs, and titanate/Au and titanate/Pd nanotube bundles were formed. In comparison with carbon nanotubes (CNTs) or active carbon that was widely used as carriers to support metal clusters, TNTs bundles can immobilize the metal clusters tightly and overcome the shortcoming of exfoliation of metal clusters from the carriers. The as-prepared titanate/metal hybrids possess mesoporosity and high surface area. The electrochemical oxidation of methanol demonstrates that titanate/Pd hybrids exhibit high electrocatalytic activity and excellent stability, and hence they should be ideal catalyst candidates in direct methanol fuel cells (DMFCs).

The controlled graft modification of Fe3O4 magnetic nanoparticles has been achieved by reversible addition fragmentation chain transfer (RAFT) polymerization under ultrasonic irradiation. The nanoparticles of Fe3O4 were first prepared by a chemical co-precipitation method, and reacted with 3-aminopropyltriethoxylsilane (KH550), and subsequently with S-1-dodecyl-S'-(alpha,alpha'-dimethyl-alpha'-acetic acid) trithiocarbonate (DDACT) to serve as RAFT agent. The graft polymerization of methyl acrylate was carried out under ultrasonic irradiation (28 KHz, 60 W). The first-order kinetics and the polymers with narrow molecular weight distributions suggested the polymerization proceeded via RAFT process. The resultant products were characterized by Fourier transform infrared spectrometer (FT-IR), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), high performance particle sizer (HPPS) and Gouy magnetic balance. The resultant products with good paramagnetism could be well modified with the "well-defined" polymers via RAFT polymerization under ultrasonic irradiation, thereby providing a new method to well modify magnetic nanoparticles.

In this paper, we demonstrated the encapsulation of CdTe quantum dots (QDs) and ZnO nanorods (NRs) with a layer of mesoporous SiO2 shell (pore size: 4.1 nm) for the purpose of integrating dual-emission property into one common nanostructure. Within the core−shell CdTe/ZnO@SiO2 nanocomposites, CdTe QDs and ZnO NRs provide visible emission and UV emission, respectively. The fluorescence intensity ratio of the dual emission can be tuned by altering the hydrolysis time of tetraethyl orthosilicate (TEOS). The core−shell CdTe/ZnO@SiO2 nanocomposites exhibit very interesting photoluminescent behaviors after interactions with heavy-metal ions such as Hg2+, Pb2+, and Cu2+. The visible emission contributed by CdTe QDs was abnormally enhanced in a range of 20−90% at the concentration of Hg2+ < 10−8 M, Pb2+ < 10−5 M, and Cu2+ < 10−6 M, whereas the intensity of UV emission by ZnO NRs was kept constant in all cases. Consequently, the UV emission may serve as a reference. The mechanism of the fluorescence enhancement is...

This manuscript describes the accurate deposition of carbon on the surface of ZnO nanorods by a simple, microwave-assisted method and the studies on the cytotoxicity and photocatalytic activity of the C/ZnO hybrids. For the coating of carbon, the surface of the preformed ZnO nanorods were first modified by amino groups and then grafted by glucose, and finally they were irradiated in a microwave field to induce the transformation of glucose into carbon. With this method, the as-prepared carbon-coated product preserved the good dispersity and uniformity of the initial ZnO nanorods. Studies on the effects of carbon-coated ZnO nanorods and pure ZnO nanorods on cultured mouse fibroblast cells revealed that the coating of biocompatible carbon remarkably reduced the cytotoxicity of ZnO nanorods. In addition, benefiting from the synergy effect of carbon and ZnO, carbon-coated ZnO NRs also exhibited excellent photocatalytic activity toward the decomposition of methylene blue in a short time (approximately 14 min).

This work describes the synthesis and magnetic–optical properties of Fe 3 O 4 nanowires decorated by CdTe quantum dots. The composite nanowires with a length of 1 μm and an average diameter of 23±3 nm were prepared in a high yield through the preferential growth of Fe 3 O 4 on CdTe quantum dots using ethylenediamine as template. Their growth mechanism was discussed based on the results of control experiments. Studies on the optical and magnetic properties of the composite nanowires reveal that they assume not only yellow-green emission feature but also room temperature ferromagnetism.

In this paper we have demonstrated that the crystallization method of amorphous colloids is convenient and feasible in the large-scale production of one-dimensional (1D) nanostructures. For the crystals with highly anisotropic structures, such as orthorhombic, trigonal, and hexagonal crystals, the crystallization generally tends to occur along the (001) axis. The preparation of orthorhombic bismuth sulfide (Bi2S3) nanorods and trigonal selenium (t-Se) nanowires by the crystallization route was used as typical examples to illustrate the process and mechanism of crystallization. The as-prepared products were characterized with transmission electron microscopy, field-emission scanning electron microscopy, X-ray diffraction, and selected area electron diffraction. Additionally, the detailed crystal growth processes involved in the crystallization of amorphous Bi2S3 colloid were investigated by studying the morphology and structure of intermediates. It demonstrates that the growth of the nanorods is through two key steps: (1) the formation of multiple activated sites on the surface of spherical Bi2S3 colloid and (2) the subsequent preferential growth along these sites.

A bio-inspired antireflective hetero-nanojunction structure has been fabricated by the hydrothermal growth of ZnO nanorods on silicon micro-pyramids. It has been shown that this structure suppresses light reflection more effectively resulting in a high photocurrent response and good charge separation simultaneously. The strategy provides a means to enhance solar energy conversion.

Supersaturation-directing self-assembly strategy for growing titanate nanoribbon membrane with capabilities of nanosolid capture and small molecule discrimination is reported. Owing to the distinct morphology of the nanoribbons and the accurate self-assembly process, the resulting membrane possesses outstanding mechanical properties (rupture strength exceeding 10 kg) and surprisingly high porosity (~97%), although there are no strong bonds among the nanoribbons. On the basis of the robustness of the membrane, we fabricated a column-shaped filter apparatus where the membrane acted as self-standing permeation barrier to evaluate its permeability and practical uses as molecule filter and nanosolid filter. The test of the membrane with pure water reveals that the membrane possesses a fast permeability while consumes very low energy due to the significantly high porosity. The test of the membrane with 13 nm Au solution and yellow-emitting CdTe QDs reveals that both the nanosolids are completely removed from the solution, indicating the membrane is an efficient nanosolid filter. The high efficiency is because the membrane is free of deficiencies and the flat and broad surfaces of the nanoribbons are ideal permeation barriers. The test of the membrane with charged molecules reveals that cationic species and anionic species are discriminated and at the same time the cationic species are enriched on the membrane, which indicate that the membrane is an ideal molecule filter too. The present work should provide a significant step forward to bringing macroscopic architectures assembled by 1D nanostructure much closer to real-world applications involving isolation and enrichment of biomolecules, catalyst reclamation, environmental remediation, and water purification. More broadly, through the on-demand capture of tiny nanosolids with optical, electrical, magnetic, and/or catalytic functionality, it is able to design and construct novel macroscopic nanocomposites readily; this will extend the applications of the titanate nanoribbon membrane beyond separation to the areas of photoelectrochemical devices, chemical sensors, catalysis, plasmonics, and so on.

Growth and alignment of nanofibers via single-step strategies are appealing goals in nanoscience studies and nanofiber-based device integration. We are inspired by the proficiency of the silkworm in manipulating one continuous thread in the space confined by the cocoon frame, and thus propose the guided growth and alignment of millimetre-long titanate nanofibers to macroscopic networks in solution by taking advantage of the unique surface properties of the periodical grooves patterned on the inner wall of a Teflon-lined autoclave. The textures of the networks can be controlled to be concentric rings or grids by tuning the geometry of the grooves. The growth mechanism of the networks is discussed on the basis of interfacial interactions. Furthermore, well-ordered networks consisting of millimetre-long heterostructured TiO2 nanofibers with an anatase backbone and monoclinic sheaths can be readily derived via the protonation and thermal annealing treatment of the titanate networks. Electrical measurements demonstrate that the heterostructured TiO2 nanofibers exhibit unique rectifying behaviours and long-range transport properties. The present bio-inspired methodology that solves the problem of growing and aligning nanofibers in solution should be applicable to other material systems. Moreover, the as-prepared titanate and TiO2 nanofiber networks may have potential applications in host–guest chemistry, thin-film based electronic and optoelectronic devices, and highly efficient photocatalysts.

Herein, we report the direct production of free-standing titanate and TiO2 nanofiber membranes with selective permeability and cleaning performance. The membrane was prepared through the hydrothermal reactions among tetra-n-butyl titanate, graphene oxide and NaOH. Tetra-n-butyl titanate reacted with NaOH to form high-quality nanofibers with lateral dimensions below 100 nm and longitudinal dimensions of several tens of micrometres. Graphene oxide was condensed with the nanofibers and enabled the nanofibers to organize into a free-standing membrane with a diameter of 1 cm. Interestingly, the interlayer of the as-prepared membrane stood parallel and as closely packed nanofibers, totally different from the disorders of those prepared by the filtration method. Benefiting from the distinctive structure, the nanofiber membrane showed a selective permeability: water could cross it easily while organic dyes and bacteria were trapped for a long time (120 h for methylene blue and methyl orange and 24 h for rhodamine B and Bacillus coli). Furthermore, the membrane showed a high efficiency in the photodecomposition of the trapped dyes because it combined the photocatalytic activity, the porosity, and the capability of separating photogenerated electrons and holes. Consequently, the membrane possesses both the separation function and cleaning function and should find potential applications in membrane-based water purification.

This manuscript describes the selective modification of ZnO multipods with a series of wide bandgap and narrow bandgap semiconductors (ZnS, ZnSe, Bi2S3, and Cu2S). ZnO multipods are firstly synthesized via the aqueous phase reaction of Zn2+ ions with KOH at a temperature lower than 70 °C, which is simple, facile and free of organic capping agents. Through the reaction of the chalcogen source (Na2S2O3 or Na2SeSO3) with the multipods supported by zinc or copper sheet, heterostructured ZnO/ZnS, ZnO/ZnSe, ZnO/Bi2S3 and ZnO/Cu2S multipods are formed. The particles of ZnS and ZnSe are selectively deposited on the tips of the multipods but Cu2S and Bi2S3 are randomly distributed on the entire surfaces of the multipods. The difference among the deposition sites of ZnS, ZnSe, Cu2S, and Bi2S3 is related to the different structural affinity of these semiconductors to ZnO multipods. The heterostructures have integrated the optical absorption properties of ZnO multipods and the deposited semiconductors, and as a result, the optical absorption range of ZnO multipods is expanded (335∼1000 nm). The photoelectrochemical properties of the heterostructures are also different from that of bare ZnO multipods. The photocurrent densities yielded by bare ZnO multipods, heterostructured ZnO/ZnS, ZnO/ZnSe, and ZnO/Bi2S3 multipods are 0.08 mA cm−2, 0.10 mA cm−2, 0.30 mA cm−2, and 0.03 mA cm−2, respectively. As for ZnO/Cu2S multipods, the photocurrent is unexpectedly smaller than the dark current.

A strategy of co-reaction of Fe and TiO2 with concentrated NaOH was designed to prepare Na2Ti3O7 nanosheets grown epitaxially by Fe3O4 crystallites, for the purpose of modifying interlayer structures and ion exchange properties of the layered compound Na2Ti3O7. TiO2 could react with NaOH to form lamellar intermediates while Fe could be converted into Fe3O4 to deposit on the surface of the intermediates. Eventually, free-standing Fe3O4@Na2Ti3O7 nanosheets were successfully synthesized in an extremely high yield (∼95% efficiency). Fluorescein and its derivatives utilized as probes to study the ion exchange property of Fe3O4@Na2Ti3O7 nanosheets, which could provide visual observations of the degree of ion exchange. The results indicate that the as-prepared Fe3O4@Na2Ti3O7 nanosheets possess much more sensitive Na+ exchange performance than isolated Na2Ti3O7 nanostructures, and hence they should have potential application in the extraction of trace active components, such as cationic amino acid and peptides in biology. Furthermore, the present strategy is also helpful in the design synthesis of other layered compounds grown epitaxially by magnetic clusters to achieve enhanced physicochemical properties.